Experimental evaluation of solid solubility of lanthanide and transuranium nitrides into ZrN matrix

The solid solution formation between ZrN and some selected lanthanide/transuranium (TRU) nitrides was examined by powder metallurgy of the nitride mixtures and simultaneous carbothermic nitridation of the oxide mixtures. The solid solubility into ZrN was determined by powder X-ray diffraction measurements as a function of relative lattice parameter difference (RLPD). The upper limit of RLPD value for the complete solid solubility was evaluated to be 8.6–8.9% in the temperature range of 1773–1973 K from the results of powder metallurgy. The solid solubility into ZrN decreases sharply in the greater RLPD value range. The solid solubility into ZrN in the products of carbothermic nitridation was lower, according to the influence of dissolved carbon impurity. The TRU composition limits for (Zr,TRU)N single-phase solid solution formation were simulated for the basis of fuel design works.